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<?php $anotherarr = array('b' => 'B'); $arr = array(); $arr['a'] = 'A'; $arr['b'] =& $anotherarr['b']; $arr['c'] = 'C'; var_dump($arr);
Output for 5.5.24 - 5.5.35, 5.6.8 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.10, 7.2.0 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.7
array(3) { ["a"]=> string(1) "A" ["b"]=> &string(1) "B" ["c"]=> string(1) "C" }

preferences:
189.76 ms | 404 KiB | 182 Q